Along with development of an Internet Protocol (IP) data network, the IP data network has become very high in expansibility, upgradability and compatible intercommunication capability. However, upgrading, expansion and intercommunication flexibility of a conventional communication network, such as a Frame Relay (FR) network and an Asynchronous Transfer Mode (ATM) network, is relatively poorer. Under limits of transmission manners and service types, a newly established network is relatively poorer in affinity, which brings inconvenience to intercommunication management. A Pseudo-Wire Emulation Edge-to-edge (PWE3) technology provides a service of transmitting layer-2 messages, such as an Ethernet message, an FR message and an ATM message, of a user on a Packet Switched Network (PSN) by deploying a Pseudo-Wire (PW) (also called a virtual link) between Provider Edges (PEs). Since the PWE3 technology can implement transmission of different services of a provider in the same network, an original access manner may be merged with an existing IP backbone network to reduce repeated network construction and reduce operation cost. In addition, the IP backbone network can be connected with diversified access networks to implement transformation and enhancement of the original data network. Therefore, these advantages of the PWE3 technology makes it applied more and more widely to various requirements and networking of the providers.
FIG. 1 is a diagram showing the reference model of a typical PWE network according to a related technology. As shown in FIG. 1, Customer Edge 1 (CE1) of a local area network 1 of a certain user accesses PE1 of a Multi-Protocol Label Switching (MPLS) backbone network of a provider through Attachment Circuit 1 (AC1); CE2 of a local area network 2 of this user accesses PE2 of the MPLS backbone network of the provider through AC2; and the provider deploys a PW for this service between PE1 and PE2. A PW is a pair of one-way Label Switch Paths (LSPs) in opposite directions. A message, sent on AC1, in local area network 1 of the user is encapsulated into a Protocol Data Unit (PDU) of the PW, and is transparently transmitted to opposite PE2 through the PW. When the message reaches PE2, PE2 locally processes and restores the message into a local form, and forwards the message to local area network 2 of the user through AC2. Message forwarding from CE2 to CE1 is similar to the process described above.
In a network environment, for various reasons, different network providers cannot establish Single-Segment Pseudo-Wires (SSPWs) between PW Terminating Provider Edges (TPEs) in respective areas, for example, for the sake of security, the providers cannot establish direct PW control channels between the TPEs in respective areas; or for the sake of expansibility, the providers adopt different PSN encapsulation technologies in respective areas; or in order to control traffic exchange among different networks, the providers adopt different PWE3 signalling protocols in respective areas. Therefore, use of Multi-Segment Pseudo-Wires (MSPWs) for implementing interconnection among the TPEs of different network providers is required. In addition, in a large-scale service provider network, a network edge may have multiple pieces of aggregation equipment, each piece of equipment may be a PE, and a bandwidth of a PW in the network may be definitely guaranteed, so that Traffic Engineering (TE) may be adopted as a PSN tunnel of the PW. Under such a condition, adoption of an SSPW architecture may increase some overhead of TE tunnel and further increase the number of PEs supporting these tunnels as well as the number of core network PEs, as a result, a service provider may divide the network into multiple PWE3 areas, and an MSPW architecture is adopted between every two PWE3 areas. In an access network and a metropolitan area network, a service provider may also adopt an MSPW architecture to improve maintainability and reduce operation cost.
There are three MSPW establishment mechanisms:
(1) Static configuration: each segment of PW is manually configured on PW Switching Provider Edges (SPEs);
(2) Path presetting: a PW path is preset, and each segment of PW is automatically spliced between the SPEs by virtue of an end-to-end signalling protocol; and
(3) Signalling-based dynamic path selection: a PW establishment path is dynamically determined by virtue of one or more dynamic routing protocols through the end-to-end signalling protocol, and each segment of PW is automatically spliced between the SPEs.
When the first mechanism is adopted for an MSPW establishment process, under a condition that each segment of PW has the same Forwarding Equivalence Class (FEC) type in an MSPW signalling process, an SPE cannot actively trigger a PWE3 signalling message to remote equipment, and the SPE can trigger the PWE3 signalling message to remote equipment of the next segment of PW only after at least receiving a PWE3 signalling message of remote equipment of a certain segment of PW. FIG. 2 is a diagram showing a reference model of a typical MSPW network according to the related technology. As shown in FIG. 2, links PW1 and PW2 which have the same PW FEC type are manually configured on an SPE, so as to establish an MSPW between TPE1 and TPE2. PW related information (including an interface parameter) is manually configured on TPE1 and TPE2, TPE1 sends a PWE3 signalling message to the SPE, the SPE resolves and stores related data (including the interface parameter) after receiving the PWE3 signalling message from TPE1, then the SPE sends a PWE3 signalling message containing the interface parameter of TPE1 to TPE2, TPE2 resolves and stores the related data (including the interface parameter) carried in the signalling message after receiving the PWE3 signalling message sent by the SPE, and performs negotiation with the locally configured parameter, and after successful negotiation, the PW is established and an LSP is formed. The process of sending a PWE3 signalling message from TPE2 to TPE1 is similar to the process described above.
Along with increase of a requirement of a user on network reliability, a provider usually needs to deploy a protection measure for a PW service to ensure that a standby PW can be rapidly found to take over the work done by the original PW when the original PW fails. Conventional PW service protection is based on a PSN tunnel level, that is, a redundancy protection technology, such as a Label Distribution Protocol (LDP)-based Fast ReRoute (FRR) technology or a ReSource Reservation Protocol-Traffic Engineering (RSVP-TE)-based FRR technology, is deployed for an outer-layer tunnel of a PW. However, this kind of protection is not enough for PPW-based end-to-end service protection. For example, the PSN-level-based redundancy protection measure is helpless to the conditions of a failure of a PW service access side, a failure of a TPE node, a failure of an SPE node and the like. Therefore, a PW service level-based redundancy protection mechanism is further proposed in the industry.
In order to protect the conditions of an AC failure, a TPE node failure, an SPE node failure, a PW failure and the like in an MSPW scenario, a CE dual-homing MSPW redundancy protection solution is adopted in the related technology. FIG. 3 is a diagram showing a scenario of dual-homing MSPW redundancy protection according to the related technology. As shown in FIG. 3, CE1 is dual-homed to TPE1 and TPE2 and CE2 is dual-homed to TPE3 and TPE4. PW11 links TPE1 to SPE1, PW21 and PW22 link TPE2 to SPE1 and SPE2 respectively, PW13 and PW14 link SPE1 to TPE3 and TPE4 respectively, and PW23 and PW24 link SPE2 to TPE3 and TPE4 respectively. Similarly, PW13 and PW23 link TPE3 to SPE1 and SPE2 respectively, PW14 and PW24 link TPE4 to SPE1 and SPE2 respectively, PW11 and PW21 link SPE1 to TPE1 and TPE2 respectively, and PW22 links SPE2 to TPE2. After PWE3 signalling is completed to form an LSP, available data forwarding paths formed from CE1 to CE2 are:
CE1-AC1-TPE1-PW11-SPE1-PW13-TPE3-AC3-CE2,
CE1-AC1-TPE1-PW11-SPE1-PW14-TPE4-AC4-CE2,
CE1-AC2-TPE2-PW21-SPE1-PW13-TPE3-AC3-CE2,
CE1-AC2-TPE2-PW21-SPE1-PW14-TPE4-AC4-CE2,
CE1-AC2-TPE2-PW22-SPE2-PW23-TPE3-AC3-CE2, and
CE1-AC2-TPE2-PW22-SPE2-PW24-TPE4-AC4-CE2.
In a stable state that no AC fails, only one LSP is selected for forwarding traffic from CE1 to CE2, and it is assumed that the path selected for forwarding the traffic is: CE1-AC1-TPE1-PW11-SPE1-PW13-TPE3-AC3-CE2. In the traffic forwarding path, effective protection as well as local convergence can be provided for a single-point failure of each node except nodes CE1 and CE2. For example, if node SPE1 fails, then the traffic path is switched to CE1-AC2-TPE2-PW22-SPE2-PW23-TPE3-AC3-CE2. If PW13 fails, SPE1 switches the traffic to PW14, CE2 simultaneously switches the traffic to AC4, and the traffic forwarding path from CE1 to CE2 is switched to CE1-AC1-TPE1-PW11-SPE1-PW14-TPE4-AC4-CE2. Therefore, in such a scenario, a failure of a single TPE or SPE node or a failure of a single-segment Pseudo-Wire will not trigger switching of the whole forwarding path from CE1 to CE2 and will only trigger local switching to implement local convergence of the traffic forwarding path, which improves switching efficiency. Even if multiple TPEs and SPEs fail on the traffic forwarding path, global switching of the traffic forwarding path can still be implemented. For example, if TPE1, SPE1 and TPE3 all fail, the traffic forwarding path is switched to CE1-AC2-TPE2-PW22-SPE2-PW24-TPE4-AC4-CE2.
In a research process, the inventor finds that interface parameters of the access side of TPE1 and TPE2 should be configured to be the same under the same service because TPE1 and TPE2 are linked to the same CE through AC1 and AC2 respectively in the MSPW redundancy scenario shown in FIG. 3. However, the interface parameters of the access side of TPE1 and TPE2 are configured by the user, so that there may exist the condition of inconsistent user configurations, which will further cause the situation that remote interface parameters of master-standby SSPWs on the same side of the SPE are inconsistent and finally cause use of incorrect interface parameters on the LSP.
A Virtual Circuit Connectivity Verification (VCCV) parameter in a PW interface parameter will be selected as an example to describe the abovementioned defect below. FIG. 4a is a diagram showing the signalling interaction in a dual-homing MSPW redundancy protection scenario when local configuration of a VCCV parameter is modified according to the related technology. The signalling interaction flow shown in FIG. 4a includes the following steps.
Step 41: TPE1, TPE2, TPE3 and TPE4 locally configure consistent VCCV values, wherein CCTYPE is 0x01 and CVTYPE is 0x04.
Step 42: in a PWE3 signalling process, PW11, PW21, PW13 and PW14 successfully negotiate and form an LSP, wherein negotiated VCCV values thereof include CCTYPE 0x01 and CVTYPE 0x04.
Step 43: it is assumed that a traffic forwarding path from CE1 to CE2 is determined to be: CE1-AC1-TPE1-PW11-SPE1-PW13-TPE3-AC3-CE2, a user expects to modify the negotiated VCCV values of the forwarding LSP to be CCTYPE 0x01 and CVTYPE 0x08 to meet an application requirement, and the user deletes a local configuration of TPE1 and reconfigures the VCCV values to be CCTYPE 0x01 and CVTYPE 0x08.
Step 44: TPE1 triggers a PWE3 signalling withdraw message to SPE1 and locally withdraws a single-segment LSP of PW11, SPE1 receives the PWE3 signalling withdraw message of TPE1, withdraws a local single-segment LSP of PW11, and triggers local switching to switch traffic from PW11 to PW21, and CE1 simultaneously perceives a failure of PW11, and switches the traffic to AC2. By now, the traffic forwarding path is CE1-AC2-TPE2-PW21-SPE1-PW13-TPE3-AC3-CE2. However, the right side of SPE1 does not perceive switching of the traffic on a left side in the process.
Step 45: TPE1 performs local negotiation based on the new CVVC parameter values to form a single-segment LSP of PW11, wherein TPE1 performs “AND (&)” operation on the local VCCV values and remote VCCV values during negotiation, the new negotiated VCCV values of TPE1 will be CCTYPE 0x01 and CVTYPE 0x00, TPE1 simultaneously triggers a PWE3 signalling message to SPE1, and SPE1 locally forms a single-segment LSP of PW11 after receiving the PWE3 signalling message of TPE1.
Step 46: the user continues deleting a PW21 configuration locally at TPE2 and reconfigures the VCCV values to be CCTYPE 0x01 and CVTYPE 0x08. TPE2 triggers a PWE3 signalling withdraw message to SPE1 and locally withdraws a single-segment LSP of PW21, SPE1 receives the PWE3 signalling withdraw message of TPE2, withdraws a local single-segment LSP of PW21, and triggers local switching to switch traffic from PW21 to PW11, and CE1 simultaneously perceives a failure of PW21, and switches the traffic to AC1. By now, the traffic forwarding path is CE1-AC1-TPE1-PW11-SPE1-PW13-TPE3-AC3-CE2. However, the right side of SPE1 does not perceive switching of the traffic on the left side in the process.
Step 47: TPE2 performs local negotiation based on the new CVVC parameter values to form a single-segment LSP of PW11, wherein TPE2 performs “AND (&)” operation on the local VCCV values and remote VCCV values during negotiation, the new negotiated VCCV values of TPE2 will be CCTYPE 0x01 and CVTYPE 0x00, TPE2 simultaneously triggers a PWE3 signalling message to SPE1, and SPE1 locally forms a single-segment LSP of PW11 after receiving the PWE3 signalling message of TPE1.
Thus it can be seen that TPE3 and TPE4 on the right side of the SPE cannot perceive changes in the local parameters of TPE1 and TPE2 in the whole process. FIG. 4b is a diagram showing the signalling interaction in a dual-homing MSPW redundancy protection scenario when local configuration of a VCCV parameter is modified according to the related technology. As shown in FIG. 4b, a user similarly performs the same configuration operation on PW13 on TPE3 and PW14 on TPE4 respectively. Such a configuration process finally causes the phenomenon that the VCCV configuration values of PW11 on TPE1, PW21 on TPE2, PW13 on TPE3 and PW14 on TPE4 are CCTYPE 0x01 and CVTYPE 0x08, while the recorded remote VCCV values are always CCTYPE 0x01 and CVTYPE 0x04, which cause the phenomenon that negotiation results of the VCCV values are CCTYPE 0x01 and CVTYPE 0x00, as a result, the opposite equipment cannot use correct interface parameter values for negotiation and PW establishment.
For a problem caused by incapability of opposite equipment in timely perceiving updating of an interface parameter of local equipment, there is yet no effective solution.